Deligne–Simpson conjecture for Coxeter connections

Let GG be a simple complex group with Lie algebra g\operatorname{\mathfrak{g}}. Fix a Coxeter GG-formal type A\mathscr{A} of slope r/hr/h with gcd(r,h)=1\gcd(r,h)=1. A nilpotent orbit threshold is a nilpotent orbit Org\mathscr{O}^r\subset\operatorname{\mathfrak{g}} such that the Deligne–Simpson problem is governed by the closure order \succeq. Deligne–Simpson conjecture for Coxeter connections. There exists a nilpotent orbit Org\mathscr{O}^r\subset\operatorname{\mathfrak{g}} such that the Deligne–Simpson problem for Coxeter GG-connections with initial data A\mathscr{A} and nilpotent orbit O\mathscr{O} has a positive solution if and only if OOr\mathscr{O}\succeq\mathscr{O}^r. Moreover, if r>hr>h, then Or=0\mathscr{O}^r=0, so the Deligne–Simpson problem always has a positive solution. This extends the preceding solution for GLn\operatorname{GL}_n-connections to simple complex groups; the candidate is stated in the source as a conjectural generalization, while the supplied parser gives no resolution evidence.

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Primary source

Maitreyee C. Kulkarni, Neal Livesay, Jacob P. Matherne, Bach Nguyen and Daniel S. Sage, “The Deligne-Simpson problem for connections on G_m with a maximally ramified singularity”, arXiv:2108.11029 (2022).

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